In the manufacture of semiconductor devices an important aspect is the production of i.c. (integrated circuit) packages by mounting semiconductor i.c. chips (dies) on support substrates such that there is good electrical and mechanical interconnection between the chips and the substrates. Among conventional techniques for mounting a chip to a substrate are wire bonding and flip chip.
In wire bonding, the chip is mounted face up on the support substrate and wire bonds are formed between bonding pads on the chip and corresponding contact pads on the substrate. In order to establish ground connection between ground points on the upper face of the chip and a ground plane in the substrate, it is necessary to form metal-plated through holes or vias extending through the thickness of the chip. The via process is low yield and renders the chips fragile and subject to breakage.
In the flip chip process, the chip is flipped face down and electrical contact pads including ground pads on the face down surface of the chip are bonded to corresponding pads on the upper surface of the substrate. Several different types of flip chip methodology are in use. One uses tin/lead solder bumps, another uses indium/lead alloy solder and yet another uses gold bumps. One main drawback of the flip chip technique is the requirement to position the chip very accurately on the substrate such that the pads on the chip are perfectly aligned with the pads on the substrate. Additionally, the resulting package often has poor thermal dissipation qualities.